SCCAsean

I have an interesting problem with my 92 Si (D16z6). For a while now, when I try and go up a hill in high gear at a lower than typical speed (high engine load) the check engine light will come on with an o2 sensor code. This happened before, the o2 sensor was replaced, and it continues to happen. It doesn't happen that often since I usually will downshift before I get in that situation and don't really notice any other performance problems. However, yesterday I was getting on an entrance ramp in the similar situation when the CEL came on and the fuel cut off for probably 3-4 seconds. The other thing I have noticed is that during the last couple of weeks (it's much warmer now, not sure if it is coincidental), it seems to be idling lower and rougher than normal (~500-600 rpm). I haven't been able to detect any vacuum leaks but that was where my first thought was, or EACV?. Anybody seen anything like this before, or have any good ideas on where to start/how to test? Thanks in advance,

Sean